Power regulator for arc furnace



atertt [72] Inventors Vitaly Viktorovich Gromakov,

ulitsa Svetlanovskaya, 22, Kharkov; Vlktor lvanovich Kapitanov, ulitsa Pochtovaya, 24, Istra; Moskovs'koi Oblasti; Anatoly Ivanovich Kitchenko, Kozjulinskaya ulitsa, 49, Kharkov; Vladimir Mikhailovich Edemsky, near Tarasovskaya ulitsa, I08, kv.9, Cherkizovo Moskovskoi Oblasti, U.S.S.R.

Appl. No. 769,902

Filed Oct. 23, 1968 Patented Dec. 15, 1970 POWER REGULATOR FOR ARC FURNACE '2 Claims, 1 Drawing Fig.

U.S. Cl 13/ 13 Int. Cl F27d 11/10 Field ofSear-ch 13/13, 13A

[56] References Cited UNITED STATES PATENTS 2,773,112 12/1956 Grebe, et a1. 13/13 2,921,107 1/1960 Toothman, et a1... 13/13 3,300,562 1/1967 Moore 13/13 Primary ExaminerG. Harris Assistant ExaminerRoy N. Envall, Jr. Attorney-Waters, Roditi & Schwartz ABSTRACT: A power regulator of an arc furnace is equipped with two drives for moving the electrode, one beinga hydraulic drive whose stroke does not exceed one-half of the stroke of the electrode and the other being an electromechanical drive whose stroke is equal to that of the electrode, these drives providing for operation of the furnace under emergency process conditions and reduction of the power consumption.

PATENTEB Dam 5 I970 POWER REGULATOR FOR ARC FURNACE The present invention relates to power regulators of arc furnaces and may be used, for example, in steel-melting and electro-slag furnaces.

Known in the prior art are power regulators for arc furnaces in which a signal from metering converters of arc voltage 1 and/or current is applied to a hydraulic amplifier (a device incorporating an electrohydraulic transducer and an amplifier). The electric signal whose value depends on the voltage/current ratio in the hydraulic amplifier is converted into a mechanical movement which serves as an input-signal of a hydraulic amplification stage. This amplified signal converted into the movement of the distribution valve of the power circuit of the hydraulic drive is used for controlling the flow of the pressure fluid which is fed to a unidirectional plunger-type hydraulic mechanism actuating the electrode. This mechanism through the elements of the device carrying the electrode moves the latter and eliminates power overshoots.

The known regulators are disadvantageous in that they are associated with great fluctuations of the input power of the furnace (great dynamic errors) due to the insufficient speed of response of the hydraulic mechanism, low-speed travel of the electrode, a large amount of fluid under pressure in the hydraulic mechanism, the presence of a considerable amount of inertia fluid in the connecting pipes, the difficulty in providing for stable operation, particularly when increasing the speed of the hydraulic mechanism for moving the electrode and the speed of response of the hydraulic drive. Furthermore, the equipment for manufacturing hydraulic mechanisms with a large stroke is very complicated.

An object of the invention is to provide a power regulator of an arc furnace which contributes to reducing fluctuation of the input power of the furnace relative to the predetermined magnitude, especially during the melting operation.

Another object of the invention is to provide high-speed travel of the electrode under emergency conditions and during manual control of the furnace.

Still another object of the invention is to provide a power regulator of an arc furnace which makes it possible to use a short-stroke two-way hydraulic mechanism.

These and other objects are achieved by providing a power regulator for an arc furnace with a hydraulic drive for moving the electrodes, which drive is connected with the elements of the device carrying the electrode and with metering converters of the voltage and/or current through a hydraulic amplifier, wherein, according to the invention, the hydraulic mechanism for moving the electrode is connected through a rigid mechanical coupling in series with an additional drive for moving the electrode arranged so that it moves the electrode through a stroke which does not exceed twice the stroke effected by the main drive, the additional drive being switched on when the hydraulic mechanism is in one of the extreme positions.

The additional drive is preferably inthe form of a step-bystep electromechanical drive. Other objects and advantages of the invention will be further described by means of an exemplary embodiment, taken in conjunction with the appended drawing the pole of which FIG. of which shows a schematic diagram of the power regulator according to the invention.

The power regulator of an arc furnace l incorporates two drives: a quick-response hydraulic drive with a high dynamic accuracy for controlling the power of the arc discharge and a conventional electromechanical drivefor a full-stroke travel of an electrode 2. v

The hydraulic drive consists of a hydraulic-mechanism 3 for moving the electrode 2 with a switching cam 4 and a hydraulic amplifier 5 (including a hydraulic amplifier and a transducer) with a distribution valve 6. 3

The hydraulic amplifier 5 is connected to a metering current converter 7 and to a metering voltage converter 8, and is fed from a pump 9 through a pressure line consisting of pipes 10 and 11 equipped with a hydraulic accumulator 12 for peak consumption and elimination of inertia of the fluid in the pressure pipe 10.

The hydraulic mechanism 3 for moving the electrode 2 is connected with the hydraulic amplifier 5 through pipes 13 and 14. Depending on the position of the distribution valve 6, the power fluid is admitted either into the upper chamber 15 or the lower chamber 16 of the hydraulic mechanism.

The discharge line consisting of pipes 17 and 18 is connected to a tank 19. This line contains a hydraulic accumulator 20 for compensating the peak counterpressure and eliminating the inertia of the fluid in the pipe 17 at the peak fluid consumption.

The hydraulic mechanism 3 for moving the electrode 2 is a two-way hydraulic cylinder and, according to the invention, designed so that it provides for a short stroke (not longer than one half of the travel of the electrode 2). The hydraulic amplifier 5 and low-volume hydraulic accumulators 12 and 20 (microhydroaccumulators) are combined into a single hydraulic unit, that is the hydraulic amplifier 5 is installed on the hydraulic mechanism 3 and the pipes 11 and 18 have a minimum length. A rod 21 of the hydraulic mechanism 3 is connected to one of the elements of the device 22 carrying the electrode 2.

According to the invention, the power regulator of the arc furnace 1 has an additional electromechanical drive consisting of an electric motor 24 and a reducer 25 and connected to the hydraulic mechanism 3 through a rigid mechanical coupling including rack 23. The additional drive operates as a step-bystep mechanism and has a stroke equal to that of the electrode In the regulation mode, the electromechanical drive is switched on and off by the switches 26, 27 and 28 mounted on one of the elements of the device carrying the electrode 2.

The operation of the power regulator is described below with reference to a single-phase steel-melting furnace.

In the initial position, after loading the charge 29, the electrode 2 is positioned above the arch 30 of the furnace 1, said furnace and the power regulator being switched 0h. The voltage converter 8 and the current converter 7 send no signals, and the distribution valve 6 of the hydraulic amplifier 5 is retained in a neutral position by the springs 31 and 32 so that the distribution valve closes the working ports 33 and 34. The pressure fluid is enclosed in the chambers 15 and 16 of the hydraulic mechanism 3, and the piston 35 remains immovable in one of the intermediate positions.

When the power regulator and the arc furnace l are switched on, a signal from the converter 8 is applied to the coil 36 of the hydraulic amplifier and the coil attracts the baffle 37 to the nozzle 38. The gap between the nozzle 38 and the baffle 37 is decreased in proportion to the number of ampere turns in the coil 36, while the gap between the nozzle 39 and the baffle 37 is increased and, as soon as the hydraulic resistance is inversely proportional to the magnitude of the gap, the pressure in the chamber 40 increases, whereas that in the chamber 41 drops.

A force proportional to the pressure drop in the chambers 40 and 41 overcomes the force of the springs 31, 32 and displaces the distribution valve to the right from the neutral position. The working port 34 is opened and the power fluid from the pump 9 and hydraulic accumulator 12 is fed through the pipes 10, 11 and 14 into the upper chamber 15 of the hydraulic mechanism 3. The piston 35 of the hydraulic mechanism 3 moves downwardly together with the elements of the device 22 carrying the electrode 2. The 'power fluid from the chamber 16 is discharged into tank 19 through the pipe 13, working port 34 and the pipes 17 and 18.

When considering this motion as steady or assuming the elements of the tank 22 to be absolutely rigid, the travel speed of the electrode 2 may be considered equal to the speed of the piston 35.

Let us denote the relative speed of the electrode with respect to the rack 23 as V Inasmuch as the hydraulic mechanism 3 is characterized by a short stroke (not exceeding one-half of the stroke of the electrode 2), the movement of the piston 35 is stopped in the extreme lower position, i.e. V, 0.

However, the switching cam 4 actuates the additional drive by depressing the switch 28 in the extreme lower position, and the electrode 2 continues to move down at a speed v, which may be called the "translational speed" of the electrode which is not equal to zero, i.e. V, 0.

This movement continues up to the moment when the electrode 2 touches the charge 29. At this moment, the converter 7 sends a signal to the coil 42 of the hydraulic amplifier 5 and, so far as the ampere turns of the coil 42 at the moment of short circuit are well above the number of ampere turns of the coil 36, the baffle 37 is displaced towards the nozzle 39. The gap between then nozzle 39 and the baffle 37 is decreased, whereas that between the nozzle 38 and the bafl'le 37 is increased. As a result, the distribution valve 6 moves to the lefi from the neutral position and opens the working port 33. The pressure fluid from the pump 9 and hydraulic accumulator 12 is fed into chamber 16 of the hydraulic mechanism 3 via the pipes l0, l1 and 13, and the piston 35 moves upward.

The power fluid from the chamber is discharged into tank 19 through the pipe 14, working port 34 and pipe 17.

From this moment, two drives are in operation: the hydrau lic drive and the additional electromechanical drive so that V, 0 and V, 0, while the absolute travel speed of the electrode 2 denoted as V, is

VI Va VI A 5 In order to provide normal operation of the power regulator during the joint operation of both the drives, the necessary condition is that the absolute value of the maximum relative travel speed of the electrode 2- {/V.,/ l max. exceeds the absolute value of the translational speed of the electrode l 1/ l max. i.e.

o/l am llVlll max.

The high speed of response of the hydraulic drive (well above the speed of response of the electromechanical drive) is a sufficient condition for normal operation of the arc furnace power regulator. In this case, the functions of the two drives are strictly different; the hydraulic drive (dynamic drive) controls the magnitude and, hence, power of' the arc discharge whereas the additional electromechanical drive (static drive) carries into effect the complete travel'of the electrode.

Since the melting speed of the charge 29 is generally slower that the translational speed V, of the travel of the electrode 2, the switching cam 4 actuates the switch 27 disconnecting the additional electromechanical d'rive, therefore, in this case V 0 while V, V,, i.e. the control of the arc discharge power is effected by the hydraulic drive depending on the relation between the signals of the converter 7 and the converter 8 within a step of the additional electromechanical drive Thereafter the functions of control of the power of the are x discharge are transferred to the hydraulic drive. Thus, during the regulation of the are discharge power, the additional electromechanical drive operates as a discrete unit, while the hydraulic drive continuously controls the arc length.

The above mentioned power regulator of an. arc furnace makes it possible to reduce fluctuations of the input power of the furnace relative to a predetermined value, particularly,

during melting operations, increase the speed of travel of the electrode under emergency process conditions and with a manual control and use of a short-stroke two-way hydraulic mechanism.

Though the present invention IS described in connection with its preferred embodiment, it is evident that modifications and variations are possible which do not depart from the concept and scope of the invention, as will be readily understood l by these skilled in the art.

These modifications and variations are to be considered as falling within the spirit and scope of the invention, as defined by the appended claims.

We claim:

l. A power-regulator for an arc furnace have a movable electrode, said regulator comprising hydraulic drive means for moving the electrode of the furnace, said hydraulic drive means including a displaceable drive member movable between two extreme positions and having a length of travelwhich does not exceed one-half the stroke of the electrode;

hydraulic amplifier means for operating said hydraulic drive means; metering converter means for measuring the furnace supply voltage connected to said hydraulic amplifier means as one input therefore; metering converter means for measuring the furnace supply current connected to said hydraulic amplifler .means as a second input therefor; an additional drive means connected in series with said hydraulic drive means to move the electrode through a stroke which does not exceed 

